Two decades after a sweeping law ushered in MCAS exams, charter schools and other major changes in the classroom, state leaders and experts say Massachusetts still has more homework to do on education reform.

This year marks the 20th anniversary of the 1993 Education Reform Act, a dramatic shift for public schools that until then had struggled with unpredictable or inequitable state funding and largely made their own rules for what to teach students.

“What constituted an A in Wellesley was very different from what constituted an A in Chelsea,” said Paul Reville, the state’s education secretary, who recently announced that he is leaving the cabinet post.

Triggered in part by a court ruling and lobbying from a business group that Reville cofounded, the 1993 law was “a revolutionary act,” he said. It greatly expanded state government’s role in education, overhauled school funding and introduced statewide learning standards and accountability measures for the first time.

While a success in many areas, the law has not solved some of the most stubborn problems in education, including a gap in achievement among students of different races, ethnicities and incomes, observers said.

“There’s no question that it is a major civil rights issue,” said Charles Glenn, a professor of educational leadership at Boston University and former director of urban education and equity for the state from 1970 to 1991.

The anniversary of the 1993 law has both policymakers and advocates considering the next generation of education reform.

To that end, Gov. Deval Patrick is seeking an increase of $550 million in education-related spending next year, with hopes of raising that figure to $1 billion annually over the next four years. He proposes to fund the increase at least in part with a percentage-point hike in the state income tax.

Nonprofit think tank MassINC is kicking off a project intended to close the achievement gap in older, so-called gateway cities and ensure that students can compete in the highly skilled Bay State economy, said research director Ben Forman.

“In ’93, we had a sense that the skills people were going to need were going to be much bigger than they had been ... but I don’t think anybody understood how profoundly the bar was going to be raised,” he said.

Business Alliance Executive Director Linda Noonan said her group will spend this year developing a new agenda for reforms. The alliance is studying everything from more individualized instruction that allows students to develop at their own pace to more rigorous teacher-prep programs.

“We really are at a defining moment,” Noonan said.

Reformers in 1993 saw Bay State schools at a crossroads and tackled changes on three fronts: financial, academic and organizational.

First, the state pumped more money into districts – Chapter 70 school aid doubled from $1.3 billion in 1993 to $2.6 billion in 2000. Changes in the state formula for distributing aid meant poorer and traditionally under-funded districts usually saw the greatest gains.

Page 2 of 3 - “The playing field between the wealthy districts and the economically disadvantaged districts was significantly leveled,” said Glenn Koocher, executive director of the Massachusetts Association of School Committees.

But some costs have since outstripped assumptions that lawmakers built into the aid formula. Special education and healthcare costs alone now exceed these estimates by $2.1 billion per year, according to the Massachusetts Budget and Policy Center.

Reville said advocates are right that this part of the school-aid formula is due for a “tuneup,” but how that is accomplished is up to the state Legislature. Part of Patrick’s proposal for additional education spending includes a $226 million increase in Chapter 70 funding next fiscal year.

On the academic side, setting rigorous standards for all subjects helped raise the bar for all students and ensured a better education across districts, several observers said.

“It allowed us ... to realign the curriculum with the (state) frameworks so that what teachers in Brockton were teaching was the same as in Weston,” said Tim Sullivan, vice president of the Massachusetts Teachers Association and a former Brockton teacher.

Many observers credit these standards for Massachusetts’ high scores on national and international assessments. Yet debate still rages on whether high-stakes exams, introduced to measure success on the standards, are crowding out non-core subjects or placing too much pressure on students.

The 1993 reform law also introduced experiments like charter schools, which receive public funding but operate more flexibly and independently than districts, and school choice.

While charters still can prove divisive, more recent reforms have sought to expand on these approaches in hopes of shrinking the persistent achievement gap.

A 2010 law raised a cap on the number of charter schools in low-performing districts, and the state has signed off on 16 new commonwealth charters since then. The state also has introduced Innovation Schools, a hybrid of charters and traditional schools, and has since approved 44 such programs.

Education officials also have redesigned state standards in math and English and are working on other subjects to align with new federal Common Core standards, which Massachusetts adopted two years ago.

That helped the state win a federal Race to the Top grant that, among other things, has helped fund new efforts in early childhood, higher education and other “connective tissue” services that might better help students with problems outside the classroom to better succeed in school, Reville said.

Along those lines, Patrick’s office said the increased funding he seeks for education would go to expanding access to preschool programs, longer school days in high-needs districts and more grants for higher education.

The state’s successes are widely admired and imitated, Reville said, “but we need to be modest enough to admit that we haven’t achieved our original goal, which was that all of our students would emerge from high school as proficient.”

Page 3 of 3 - “That isn’t the case now, and that’s why we have a long way to go,” he said.